Electrical machine of the vertical type with a housing of concrete



June 4, 1968 J. MUCKE 3,387,152

ELECTRICAL MACH OF THE VERT L TYPE WITH A H0 NG OF CONCR E Filed Jan. 29, 1965 2 Sheets-Sheet 1 iF'ig.2

June 4. 1968 J. MUCKE 3,387,152

ELECTRICAL MACHINE OF THE VERTICAL TYPE WITH A HOUSING OF CONCRETE Filed Jan. 29, 1965 2 Sheets-Sheet 2 United States Patent 9 Claims. 6|. 310-89) ABSTRACT OF THE DISCLOSURE Electrical machine of the vertical type includes a stack of stator laminations forming a closed ring structure capable of resisting tangential tractive forces, a concrete housing comprising a wall surrounding the stack and ha-vouter surface, rod-shaped reinforcing struts spaced uniformly along the periphery of the stack, the struts having a spoke-like arrangement, each of the struts extending with clearance through passages formed in the concrete housing wall and anchored by one end thereof directly to the concrete housing wall at the outer surface of the wall, and connected by the other end thereof to the stack, the concrete housing wall being under compression and the struts and the stack being under tension.

My invention relates to electrical machines of the vertical type that are equipped with a housing of concrete and with a stack of stator laminations joined with the concrete housing by reinforcing struts uniformly spaced from each other along the stator periphery.

During the operation of such machines, particularly waterwheel generators, considerable tangentially and radially directed forces may be produced that have to be taken up by the foundation or by the housing connected therewith. Such forces are caused, for example, by heating, by the torque or by the magnetic flux during operation of the machine.

It has been proposed to employ tensioning bolts as reinforcing struts between the stator stack and the concrete housing. These bolts are rod-shaped and extend in crosswise relation to each other, their points of intersection being anchored in the concrete with the aid of set screws. By such an arrangement, the frame work-like braces may be subjected to tensioning and compressing stresses due to tangential forces, with the result that the set screws are subjected to shearing forces and in some cases also to bending forces in the radially outward direction. Such radially outward forces produce detrimental, tangentially directed tensile stresses upon the concrete material. The set screws for anchoring the struts in the concrete are guided in steel tubes. The insertion of the steel tubes prior to casting the concrete or into openings provided in the previously prepared housing of concrete, as well as the accurate fastening of the tubes, requires greatly accurate measurements which can scarcely be obtained by inexpensive means. The tangential forces transmitted from the assembly of struts upon the set screws act through the steel tubes predominantly upon the inner marginal zone of the concrete housing and produce in this inner zone locally high and thereby detrimental stresses acting upon the concrete material.

It is an object of my invention to minimize or eliminate the above-mentioned detriments and to devise an electrical machine of the above-mentioned general type in which the concrete housing, during operation of the machine, is essentially stressed only by compression and the stack of stator laminations is essentially stressed only in tension.

According to the invention, the stack of stator laminations of the machine is formed as a closed ring structure resistant to tangential tractive forces, and the rod-shaped reinforcing struts to be subjected to tension are arranged in spoke fashion and are directly anchored in the concrete housing.

According to another, preferred feature, it is particularly advantageous to have the rod axes form tangents with respect to the peripheral surface of a geometrical, imaginary cylinder coaxial to the stator lamination stack, the cylinder diameter being smaller than the outer diam eter of the stack. The rods are arranged, for example, so that each rod crosses at least one of the other rods. Since each individual reinforcing rod is anchored in the concrete or on the outer side of the concrete structure in prestressed condition, the reinforcing struts can be stressed only by tensile forces. Thus, there results an inherent condition of tension in which the concrete housing acts as a closed pressure arch or vault and the stator lamination stack acts statically as a pull ring. The rods anchored on the outside of the concrete housing may be freely located in the interior of envelope tubes whose inner diameter is larger than the diameter of the rods so that the intermediate clearance permits directional deviations of the rods.

According to another feature of the invention, the anchoring of the rods on the outer side of the concrete housing is effected by bell-shaped anchoring bodies which are embedded into the concrete from the outside. These anchoring bodies form the only force-constrained connection with the concrete housing so that it is not necessary to subsequently press cement mortar into the joint. The ends of the strut rods may be anchored within the concrete in several parallel layers and may be secured to the stator lamination stack at suitable positions parallel to one another on different levels. Of course, the reinforcing rods may also be arranged radially so that the axes of the rods intersect layerwise at a point on the machine axis. However, since in the latter case the rods can take up only radial forces, it is necessary that at least one of the pressure plates which hold the lamination stack together be anchored in the foundation or in the concrete housing which normally forms a unit together with the foundation. For fastening the rods, a screw thread may be rolled onto both ends of each rod, for example.

For introducing tension into the reinforcing rods, it is preferable to employ hydraulic devices. These devices may be uniformly distributed over the periphery of the concrete housing and may be force-transmittingly connected stepwise, one after the other, with a corresponding number of reinforcing rods. During the prestressing operation, the hydraulic devices are controlled from a single controlling location and simultaneously as well as uniformly actuated, if desired, with the aid of process computers or monitors.

The invention will be further described with referenceto embodiments of machines according to the invention illustrated by way of example on the accompanying drawmgs.

FIG. 1 is a fragmentary view of an axial section through the stator of a vertical-type electrical machine and the appertaining concrete housing.

FIG. 2 is a partly sectional top view of FIG. 1.

FIG. 3 is a partly sectional view of another machine according to the invention, similar to FIG. 1 but equipped with a different arrangement of reinforcing rods; and

FIG. 4 is a partly sectional plan view of the machine according to FIG. 3.

The machine shown in FIGS. 1 and 2 comprises a laminated, ring-shaped stator 1 which is surrounded by a housing of concrete consisting of a ring-shaped concrete wall 2 and a foundation 3 integral with the wall 2. The lamination stack 1 is held together by ring-shaped pressure plates 4 and 5 and is supported on the foundation 3 by means of a carrier assembly 6.

The stack may be formed, for example, by a single pile of identical laminations. The connection of the stack with the concrete wall 2 is effected by tensioning rods 7, 8 in a spoke arrangement. In this particular embodiment, the geometric extensions of the rod axes form respective tangents to the peripheral surface of an imaginary cylinder whose diameter is smaller than the outer diameter of the stack 1. The rods 7 are arranged in two different levels and the appertaining rods 8 are slightly spaced from the rods 7 so that the peripheral surfaces of each two rods 7 and 8 either just touch each other or are only slightly spaced from each other.

As shown in FIG. 2, one tensioning rod 7 and one tensioning rod 8 are fastened to the same point of the lamination stack 1, and the fastening points are so close to each other that each rod 7 extends across four rods 8 and conversely each rod 8 passes across four rods 7. The rod portions extending in the concrete wall 2 pass through respective envelope tubes 9 whose inner width is considerably larger than the diameter of the respective rods. Consequently, the rods have sufficient clearance in the envelope tubes, and the tubes 9 can therefore be readily embedded into the concrete when the housing wall is being produced, without any exacting requirements with respect to accurate measurements. Furthermore, when casting the concrete wall, bell-shaped anchoring bodies 10 are likewise embedded therein for the purpose of anchoring the tensioning rods 7 and 8. It is preferable to arrange two anchoring bodies 10 for the rod 7 and the adjacent rod 8 within a single recess 12 in the outer peripheral surface of the concrete structure. The ends of the tensioning rods 7 and 8 are provided with a rolled thread, to receive respective nuts 11. The concrete wall may be produced of prestressed concrete without other reinforcements. For joining the lamination stack 1 with the concrete Wall, the tensioning rods 7 and 8 are passed through the envelope tubes 9, then fastened to the lamination stack, placed under tension with the aid of hydraulic devices and ultimately fastened and tightened by means of the nuts 11. A type of reinforcing arrangement shown in FIG. 2 requires the use of at least four hydraulic devices, namely two devices from each of diametrically opposite sides of the housing. In cases where the outer side of the concrete wall is not accessible, the tensioning rods, inclusive of the nuts placed upon the rods and inclusive of the anchoring bodies and enveloping tubes shoved upon the respective rods, are embedded in the concrete when the ringshaped housing wall 2 is being produced. In such case, a small hollow space is provided above the anchoring body wherein the nut-carrying end of the rods can freely move. By virtue of the enveloping tubes, the requirements as to accuracy of alignment can be maintained without any difficulties. With this type of construction, the reinforcing rods, after being prestressed in tension with the aid of hydraulic devices, are subsequently fastened to the lamination stack 1.

The machine shown in FIGS. 3 and 4 is to a large extent similar to that of FIGS. 1 and 2, the same reference numerals being employed for corresponding components respectively. The tensioning rods 13 are arranged at two different levels and extend radially, that is, they intersect in layers at two respective points of the shaft axis of the machine. In lieu of the bell-shaped anchoring bodies according to FIGS. 1 and 2, the machine shown in FIGS. 3 and 4 is provided with substantially discshaped anchoring bodies 14. Due to the radial arrangement, the tensioning rods 13 can take up only theradial pulling forces. Tangential forces in this embodiment are transmitted through the carrier assembly 6 or through the supporting spider 15 to the foundation, to be taken up thereby.

By virtue of the prestressing in tension to which the reinforcing rods are subjected and which is at the highest obtainable value, the concrete housing and the lamination stack constitute a mechanical unit and, on account of the high natural frequency of this unit, are substantially insensitive with respect to all vibrations occurring in normal practice. The reinforcing rods and the lamination stack are stressed only in tension, and the ring-shaped concrete housing only in compression.

To those skilled in the art, it will be obvious upon a study of this disclosure, that my invention permits of various modifications with respect to design and arrangement of components and hence may be given embodiments other than particularly illustrated and described herein Without departing from the essential features of the invention and within the scope of the claims annexed hereto.

I claim:

1. Electrical machine of the vertical type, comprising a stack of stator laminations forming a closed ring structure capable of resisting tangential tractive forces, a-concrete housing comprising a wall surrounding said stack and having an outer surface, rod-shaped reinforcing struts spaced uniformly along the periphery of said stack, said struts having a spoke-like arrangement, each of said struts extending with clearance through passages formed in said concrete housing wall and anchored by one end thereof directly to said concrete housing wall at .said outer surface of said wall, and connected by the other end thereof to said stack, said concrete housing wall be ing under compression and said struts and said stack being under tension.

2. Electrical machine according to claim 1, wherein the axes of said struts are tangential to the peripheral surface of an imaginary cylinder located coaxial to said stack and having a diameter smaller than the outer diameter of said stack.

3. Electrical machine according to claim 2, wherein each strut crosses at least one other strut.

4. Electrical machine of the vertical type, comprising a stack of stator laminations, pressure plates for holding said stack together to form a closed ring structure capable of resisting tangential tractive forces, a concrete housing comprising a wall surrounding said ring structure and having an outer surface, rod-shaped reinforcing struts spaced uniformly along the periphery of said ring structure, said struts having a spoke-like arrangement, each of said struts extending with clearance through passages formed in said concrete housing wall and anchored by one end thereof directly to said concrete housing Wall at said outer surface of said wall, and connected by the other end thereof to said ring structure, said concrete housing wall being under compression and saidstruts and said ring structure being under tension.

5. Electrical machine according to claim 4, wherein said closed ring structure has a longitudinal axis, and said struts are located in layers at different levels respectively, the longitudinal extensions of the struts in each layer intersecting at a common point on said axis of said closed ring structure.

6. Electrical machine according to claim 4, wherein said concrete housing includes a foundation wall, at least one of said pressure plates being anchored to said foundation wall.

7. Electrical machine according to claim 1, wherein said reinforcing struts have threaded ends, and including internally threaded anchoring means embedded in said 5 6 outer surface of said concrete housing wall and threaded the diameter of said rods so as to provide clearance thereon said threaded ends of said struts respectively. between.

8. Electrical machine according to claim 7, including References Cited enveloping tubes in the WaH'Of Said COHCIBPe P housing, said reinforcing struts extending through said 5 tubes, said anchoring means being in the form of bell- 3,293,464 12/1966 P 310' 89 shaped anchoring members for holding said struts re- I spectively to said wall, MILTON O. HIRSHFIELD, Przmary Examine).

9. Electrical machine according to claim 8, wherein the L. L, SMITH, Assistant Examiner. inner diameter of said enveloping tubes is greater than 10 

